.NET Framework 3.0: x64 (KB928416) can't install via Microsoft Update

ON both a new/clean install of XP Pro 64-bit and Server 2003 R2 64-bit,
the Microsoft Update subsystem cannot install the Framework 3.0 for
64-bit platforms. In both systems, the problem appears to be related to
the installer command string that is being used my Microsoft Update (in
addition to failing in MU, the dotnet update shows the Windows Installer
[msiexec] dialog box with the available arguments).

I had the same problem with the package downloaded via WSUS.
I downloaded the distribution package from the the .net site, which then
detected x64 and downloaded the correct parts and installed it correctly.
(It shows in add/remove programs as installed, although I haven't tested it
yet).
However, at this point Windows Update still thinks that it needs to be
installed and getting the problem you describe. Does anybody know how to
make Windows Update recognize that this update has actually already been
installed?

I can't install in on Windows XP Family (French) 32 bits.

I always get an error message asking me to try again.